text:
Why would a jet engine that runs at temps excess of 2000°C burn when it crashes?
Airline engines are designed to work at very high temperatures. Yet, when a plane crashes they're burnt (see below). Is it something in their design?

(bostonherald.com)

The engine in the photograph is not melted.

I have to challenge the premise.  From the picture, it looks like the external housing of the engine burned and/or melted.  The internal parts look like they've just suffered impact damage.  The external housing does not experience high temperatures.  Same reason the combustion temperature of your car's engine may reach 2000 C or so, yet the plastic components sitting nearby don't melt.

related: https://aviation.stackexchange.com/a/16842/1467

I think that the only thing we can say about the external housing is that it is missing from the picture.  Besides melting or burning away it could have broken up on impact and pieces shed away as the core slid along the ground.  Tough to surmise what happened from a single still photo.

How The Jet Engine Works:

Inside the typical commercial jet engine, the fuel burns in the combustion chamber at up to 2000 degrees Celsius. The temperature at which metals in this part of the engine start to melt is 1300 degrees Celsius, so advanced cooling techniques must be used.

You can read more about some of those cooling mechanisms in How are temperature differences handled in a jet engine?
See also, How do you stop a jet engine melting?:

Neil - The normal melting point of the nickel blade alloys that we use in the turbine is typically about 12-1400 degrees. But what you do, and this is the clever bit, is you actually cool these blades. You have internal cooling passages, which effectively has air that flows through and it's about 7-800 degrees. And this cooling air then exits from small little minute holes that have been drilled on the surface of the blade and this air then forms a kind of a film on the surface of the blade, and this technology is typically called a 'film cooling.'
What you also do - you coat these blades and typically use something called a thermal barrier coating. The thermal barrier coating, effectively, is ceramic, typically about quarter of a millimeter in thickness, but they have got very, very low thermal conductivity. So, effectively, even though the gas stream is at a much higher air temperature, the effective metal that exists beneath the thermal barrier coating is much colder, and you get thermal grade of the order of about 100 degrees C between the hot and the cold surface. So all of this put together - this whole cooling technology effectively helps to keep the blade below its melting temperature.

The engine is designed to manage the intense heat in a controlled way, by restricting it to certain components, injecting cool air around the hot parts, and choosing different materials for different parts of the engine. If the engine is severely damaged, doused in jet fuel, and set on fire, none of those mechanisms function; the entire engine (or whatever is left of it), as opposed to just the portions intended to manage heat, will be hot, and none of the cooling mechanisms will be working.

Those blades are little marvels of engineering. Something you can hold in one hand but costs some ~5000 dollars (and there's a whole lot of them in one turbine)

Just out of interest, @mbrig , is it actually ok to hold in your hand (and then safely use)? I know its robustness would point one way but the way it's been micro-optimised for a different environment might indicate the opposite. I know, for exmaple, quartz envelope bulbs rather dislike skin oil: I don't mean this in particular, but this kind of thing.

@Dannie I wouldn't know unfortunately, the one I got to hold was from an areo-derivative generator that had been rebuilt, and wouldn't be going back into use either way.

@Dannie Yes, turbine blades can be handled with your bare hands and used. The metals are nickle based super alloys and they sometime have a ceramic thermal barrier coating they are very environmentally stable. When assembling an engine, they actually use beeswax to hold seals in place and it just burns off once the engine is ran.

I'd like to add, that although the superalloys can make it to ~1400C before they melt, they will oxidize ("burn") at lower temperatures. The picture to me looks mostly like impact damage to me with some oxidization. Part of the reason it looks like impact damage to me is that materials with low melting/oxidation points are still there, but then materials with very high melting points are not.

So you're telling me that a jet engine actually operates above the melting point of the turbine blades? And that they are kept solid by some sophisticated aerodynamics? And if that fails, the entire engine will presumably turn into a blob of lava? I wish I hadn't read that now...

@OSUZorba it's even cleverer than that.  The surface isn't the same as the bulk, but a thin layer of nickel aluminide (some blades anyway) with a high thermal conductivity and high melting point (~1600-1900C).  This reacts in service to form Al2O3 (sapphire), MP ~2000C, but if blades are overhauled the sapphire must be removed before recoating. Paper from some former colleagues of mine.  I've handled the blades in question, which I believe were miltary.

@OscarBravo Yes, the gas path air can be nearly 2000F above the capability of the materials it is interacting with. The cooling isn't really aerodynamics, but a system of using compressor bled air to actively cool the materials. While the designing the cooling is very complex, the operation is very simple. There are just a series of orifices and metering holes that allow a specific amount of air through at each point. There are no valves or other moving parts to fail. Of course, there have been failures but generally the airfoils oxidize away before they melt.

@ChrisH Yes, that is correct. Every HPT airfoil I ever worked on had a surface coating, even if it didn't have TBC, although not the specific one you mentioned. It was used for environmental protection, but it was too thin to really help with cooling the base material.

Peter's answer to another question has a nice chart that shows internal jet engine temperatures:

You can see that the temperatures are highest by a fairly large factor in the combustion chamber. This means that only the combustion chamber needs to be able to withstand those temperatures. To save weight and often use less expensive and less exotic materials, the rest of the engine may be made out of materials that don't need to withstand such high temperatures. As such, in an accident where jet fuel may be dispersed in an uncontrolled way and burn with as much oxygen as it can get, it's easy to scorch engine parts and anything else around.
It also is in part a question of time. The ability to withstand heat varies with time. In a crash of a fairly fueled aircraft that may burn uncontrolled for a long time you are likely to find scorched parts like this. Whereas a plane that runs its tanks try and crashes in a field may not see the same fire marks. However, if the plane hits the ground with enough force the heat generated from the impact can also lead to markings like this.

First off, the engine is running around 2000° F (NOT 2000° C/3632° F) only in a few places within it.  The Turbine Inlet Temperature (TIT) can be that high but cools rapidly when the exhaust gases are rapidly expanded through the high and low pressure turbines to exit at approx 1000° F at the jet pipe (enthalpy is converted into mechanical work here).  Most sections of the engine are not designed for that high of a temperature and may well oxidize or deform in the post crash fire.
UPDATE:  While I do not have definitive values for the max TIT of a CFM-LEAP engine, a good estimate would be around 1500°- 1600° C (2732° - 2912° F) as this represents about the state of the art for gas turbines outside of a few military applications.  This source quotes that the Pratt & Whitney F-135 can operate at TITs of 2000° C due to its use of a proprietary ceramic coating over single crystal nickel cobalt superalloys for the hot section.  It is unclear whether that is a sustained engine power setting or simply a max operating temp prior to destruction.  This is NOT representative of a typical aviation gas turbine, which run much cooler.  I would stand by my original figure of 1000-1200° C TIT for earlier gas turbines eg PT-6, J85, J79, etc.

Note: 2000° F is 1093° C

.....what is your point?

@CarloFelicione probably to inform people like me what the celsius equivalent to 2000° F is (seeing as celsius is something you provide for the other value, and most of the world understands over fahrenheit)

This disagrees with the temperatures quoted in other answers.

No it does not. Tf = 9/5 * Tc + 32

This does disagree with the answer by Zach Lipton which quotes a source as stating "2000 Celcius" (and links the source).

Do you have a citation for this figure? The Stanford link that Zach quoted above specifically states "up to 2000 degrees Celsius", and the chart posted by Dave appears to peak at around 1788 degrees Celsius (~3200 F).

My source, which uses vague "up to" language, is from a course about WWII, so I wouldn't treat it as authoritative on the details of every engine today. Here's another source that says 1400°C and here's an FAA manual that says "around 4,000º F" with a cooler airmass around it. It also depends greatly where you measure, as the entire point of the cooling system is that the hottest temperatures are only found in one place.

Turbine inlet temperatures on modern engines are over 2000C, far beyond 2000F. The materials used in modern turbines could survive uncooled at 2000F, yet they all have very expensive (in design and engine efficiency) cooling. The LEAP uses extremely high combustion temperatures, in the high 3000sF. The shrouds are CMC and still have to be cooled.

I also want to state the every modern jet engine at least since the late 60s has used single crystal nickel cobalt superalloys for the hot section and most use TBC coatings. The LEAP even uses CMCs that have much higher temperature ranges than the nickel superalloys. The F-135 is not the hottest engine around.

Evidence to back this up?

@CarloFelicione Considering the Turbine Exhaust Temperature redline for the Leap-X is 1900F, which is after the HPT expands and cools the gas, I think that is a pretty good indication your numbers are off. Type Cert here: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/ae71cf81844093f98625836600766d81/$FILE/E00088EN_Rev_4.pdf I also have six patents on turbine cooling designs, but can't quickly find public data on T4 temperatures.

Yeah I’ve read the type cert.  That is pretty high, though if I recall the max continuous operation EGT is a chillier 1700° F or so.  If they are getting those kinds of CET/TITs, that’s amazing as the current state of the art is about 1700° C.


text:
How energy efficient is an aircraft take off?
How much work is generally done by an aircraft (e.g. B737NG) in order to reach V_rotate, and how does this compare to the energy content of the fuel that is used?

Welcome to aviation.SE. This looks like an assignment. What have you tried? What exactly do you need help with? what do you mean "how does this compare to the energy content of the fuel" ?

You can determine this by measuring fuel consumption to reach Vrotate (factoring in head, tail, or no wind). Power would be full or close to full, so check fuel burn rate under those conditions and average time to reach rotation speed. That should get you close.

You can make a decent approximation with very basic numbers. Take for example the CFM56-7B (which is incidentally also used on the 737NG).

Maximum thrust specific fuel consumption $TSFC$ at takeoff: ~10.9 g/s/kN
Maximum thrust $F$ at takeoff: 121 kN
Jet fuel specific energy $e$:  43 MJ

Combining these figures gives a fuel burn of 1.4 kg/s at takeoff, or 57 MJ of chemical energy released every second ($P=57MW$).
To get an airplane of mass $m$ to a certain speed $v$, it needs $$E=\frac{1}{2}mv^2$$ of kinetic energy. It does so in $$t=\frac{v}{a} = \frac{vm}{F}$$ seconds (remember, $F=ma$). The efficiency $\eta$ is useful work done $E$ divided by input energy ($Pt$),
$$\eta =\frac{mv^2}{2Pt} = \frac{vF}{2P} = \frac{v}{2\cdot TSFC \cdot e}$$
Immediately, we see why TSFC is an important figure. Plugging in some numbers, let's say $V_R =145\mathrm{kts} \approx 75\mathrm{m/s}$, we get a total efficiency of $\eta \approx 8\%$ until rotation.
Note that this calculation assumes constant TSFC while in reality it is very much a function of $v$ (indeed, with this calculation you could have $\eta>1$ if $v\to\infty$ which is clearly impossible).

Now you've made me wonder what would happen if someone were to combine these calculations with the special relativity colinear velocity addition formula...

@aCVn Nothing interesting I'm afraid. The situation I sketch is similar to a small rocket being fed fuel from an impractically huge rocket travelling alongside it - it would approach light speed but never reach it, and be infinitely efficient because I'm not counting the energy expended by the impractically huge rocket.

What would happen with the efficiency if an electric engine would be used instead of the CFM motor? (considering instant available torque and higher efficiency of the motor)

@JNld Your batteries run out quickly. But apart from that, it's mostly down to the difference between a propeller engine (constant output power at constant input power) and a jet engine (constant output thrust at constant input power). Again, those are first-order approximations. You will find that a propeller, electric or not, is much more efficient at low speed. You can find the equation for propeller efficiency here

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
What is a 73W aircraft
With all the issues surrounding the Ethiopia crash can you tell me what a 73W is?  Is it a 737 Max 8.  We're trying to figure out if our flights with Westjet on Friday might be effected.
Thanks
Frank N

It won’t be affected as you won’t be flying on a 737 MAX then.  Both the FAA and Transport Canada grounded all 737 MAX flights in their respective jurisdictions.

According to https://www.airliners.net/forum/viewtopic.php?t=241063 (and others) B73W is a newer version of Boeing 737-700. A one with winglets installed.
So, it's not B737 MAX 8.
A more comprehensive list (which sadly does not include 73W) is here What is the difference between Boeing 73G, 73H and 737?.

@ymb1 Might not change the fact :D

73W describes a 737-700 with winglets. This is an older model and not a 737 MAX model. It is not covered by recent regulatory actions.
Most of Westjet's fleet is not impacted, though they will be shuffling flights around to different aircraft types, so there's no guarantee your flight couldn't see some effects, but it should be less likely.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Are the holes inside the engine nacelle used for uniform intake of air?

I read the post here: What is the function of the holes in splitter plates?
My question is, what are those hole looking things inside the engine nacelle?
It seems reasonable to me that as air enters the intake slower air would accumulate towards the outboard portion of the engine nacelle due to the shape of the leading edges. You want the air to enter the blades uniformly so you could add these pinholes which would remove the slower moving air. This would lead to more even distribution of faster moving air and subsequently better engine performance.
Am I tracking correctly?
Edit: here’s another picture

They are for reducing noise emissions. According to Wikipedia,

Liners are applied on the internal walls of the engine nacelle, both in the intake and by-pass ducts, and use Helmholtz resonance principle for the dissipation of incident acoustic energy.

The Helmholtz principle (Wikipedia again) can be watched (or rather heard) when blowing over a bottle which produces a sound.

Helmholtz resonators are also used to build acoustic liners for reducing the noise of aircraft engines, for example. These acoustic liners are made of two components:
  a simple sheet of metal (or other material) perforated with little holes spaced out in a regular or irregular pattern; this is called a resistive sheet;
  a series of so-called honeycomb cavities (holes with a honeycomb shape, but in fact only their volume matters).
Such acoustic liners are used in most of today's aircraft engines. The
  perforated sheet is usually visible from inside or outside the
  airplane; the honeycomb is just under it. The thickness of the
  perforated sheet is of importance, as shown above. Sometimes there are
  two layers of liners; they are then called "2-DOF liners" (DOF meaning
  Degrees Of Freedom), as opposed to "single DOF liners".
  (Wikipedia)


text:
In the compressor characteristic, how do I calculate the minimum flow?
I have a small question, how do I determine the minimum flow point on the compressor characteristic? I.e. what is the safety margin on the curve?


text:
In 1924, why did aviators use an oak propeller for pontoon aircraft and walnut propeller for wheeled aircraft?
The year 1924 marks the first circumnavigation of the globe by aircraft.  In a recent podcast, a former employee of the National Archives remarked that the Army aviators planned to use an oak propeller when the aircraft was configured for water landing (on pontoons) and a walnut propeller when the aircraft was configured for terrestrial operations (wheels).  (The comment occurs at elapsed time 01:14:58 in Episode 197, "World Flight Centennial, 1 of 3 - Build Up", September 16; accessed 20241001).

Why was the propeller changed?
Why was a different wood used?
Why were these woods (oak, walnut) chosen for these kinds of operations?

Related, not a duplicate: What types of wood can be used for making propellers?. See also Basic Propeller Construction - Materials, ca. 1920.

Like most of tools: you choose the right wood for the right job (and often several wood on same tool). No material is perfect. I assume one is lighter, but the other is more water / salty resistant (aka: expand less when wet). And you need wood well known for tools (and construction), with people that can work it correctly, they can get it easily

This has to do with the properties of the wood: oak and walnut are both strong, non shrinking and resistant to warping.
Oak is a heavier and very water resistant. Walnut on the other hand, while lighter, cannot handle moisture very well.
Ever since the very beginning aviation has been "weight sensitive", hence the optimization.

This answer would be stronger with a reference that shows early aviators understood your comments about the quality of the wood.  Scientific American suggests that walnut was used because it was common, and oak was simply a more economical replacement.  The same article suggests that the glue holding the layers together was "not water proof." https://www.scientificamerican.com/article/white-oak-works-best-for-fighter-plane-propellers/#:~:text=Quarter%2Dsawn%20white%20oak%20combat%20propellers%20were%20put,and%20under%20extreme%20conditions%20of%20humidity%20the

I can try to dig something up, but I'm certain beyond a shadow of doubt that the professionals of early 1900's were well versed in properties of types of wood. Carpenter is one of the oldest trades with thousands of years of tradition.

@Jpe61: Besides that, early water-landing aircraft drew heavily on boatbuilding techniques, which were certainly very well aware of how different woods would interact with water.

Just to elaborate. White Oak is water-resistant. The more common (?) red oak, often used in furniture and interior flooring, is not.


text:
Why are Jet Engine fan blades (and other turbomachinery blades) cantilevered rather than being connected together at their outer edges?
It seems to me that connecting the outside edges of each blade together would create a stiffer structure with lower stresses and a better fatigue life for a given operating condition.

The reason is probably different, but joining the outside edges with a sort of ring will increase a lot the m. of i., and the turbine will be less responsive to changes...

I'd imagine the consequences of a ring failure would be more serious, too. If one independent blade breaks, it (simplistically) just flies away.  If the ring cracks, it could take a large chunk of blades with it, creating serious imbalance &c,

@xxavier Yeah that makes sense, I didn't think of that. Also, I don't think my question is a duplicate of the one posted. Mine is to do with the attachment points of the blades, not why the blades are loosely attached at the base. What is the proper way to challenge what I believe to be a false duplicate?

Well, this is actually a different question. Long turbine blades, which usually have a short chord, and so a long blade has a high aspect ratio, often are connected at the tips with a shroud. Typically this is done for the last few turbine stages, which are significantly longer than the early stages. And fan blades in early engines sometimes had a mid span shroud, which supported the blade, in much the same way. In both cases this is done for exactly the reasons you mention.

@jamesqf: If the ring cracked, it would still be held on by all those blades connected to it.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
What is the altitude of the nose vs tail in airplane flight?
Suppose you have an airplane flying level on a long flight. Now suppose you place one altimeter sensor in the tail, and one in the nose. Suppose you record and store these values independently (perhaps take 10 readings per second.)
And then suppose you graph this data.
This is the graph i'm looking for. Has anyone ever seen data like this?
In other words, i'm looking for experimental data which has logged a comparison of the altitude of the nose, vs. the altitude of the tail, (several times per second) on a long flight.
The intent is to study how the pitch of the aircraft is constantly in flux -- e.g. by turbulence, wind speed changes, the curvature of the earth, and (of course) by the pilot's inputs themselves, etc.

why don't you directly look for graphs/data of the pitch?

Different planes have different flight attitudes. And the sensors that you mention may be placed in the tail and on the nose, but where exactly...? Because 'the tail' or 'the nose' aren't points...

"why don't you directly look for graphs/data of the pitch" Yes, the instance of pitch data, with a high sample rate, would be fine. I can't find any though.

"Because 'the tail' or 'the nose' aren't points" In other words, i'd like the sensors to be as far back and as far forward as possible.

Yes that data exists , it is recorded during flight test data gathering for full flight simulators. The transducers used are not two bars altimeters, but direct gravitational angle finders and gyro's for increased frequency response. Sample rate was 30 Hz in the olden days, now 100 Hz or higher.
A full set of measurements consists of correlated sets of

pitch, roll, yaw angle measurements from dedicated mounted transducers;
angle of attack and sideslip, dynamic and static pressure, magnetic course, and all other parameters recorded by the aircraft instruments;
stick and control surface positions from dedicated mounted transducers.

The aircraft data sets are sold for a lot of money, your best bet would be to try to get your hands on flight data measurements for an older type aircraft or a type that is not produced anymore.
Next time you fly, you could even measure this yourself by using the transducers in your mobile phone, which has acceleration, rotational velocity and angle transducers, plus a set of linear GPS co-ordinates.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Do Military Turboshaft engines have a distinctly different sound from Civilian ones?
I live in India, and near an airbase so there are a moderate amount of helicopters flying overhead. My friend claims that he can distinguish between a civilian helicopter or a military one based on the engine noise. He says that military helicopters have a higher pitched whine in their noise that is absent from civilian ones. I have heard it myself but I have no idea if it's perception after he told me or reality. Is there any truth to this? Keeping in mind that most military choppers are Russian/Soviet designs in India while a lot of civilian choppers are Bells

I think the real answer is different engines sound different regardless whether they are military or civilian. And since most of the sound emanates from the inlet and exhaust, the same engine on a different helicopter can sound vastly different. The shape, length, structure, and orientation of the ducts will have a marked effect on the sound of a helicopter.

This question is kind of vague, I'll explain why: your question asks about military turboshafts in general, but on civilian models that are converted to military types generally keep the engine. Granted, armoring, small modifications regarding battlefield/military use will be made, but they are the same in the big scheme. On the flip side, these modifications can indeed change the sound if they influence sound output sources, like exhaust shielding for lower IR signature, etc. If you could be more specific, like troop transport, recce, etc helo engine noise then you could get a better answer.

I think your friend is playing a joke on you. I have worked with helicopters since the late 1970's and there is no way to distinguish military from civilian simply by engine noise. You may be able to distinguish between models of helicopters, and in so doing identify a model used by the military versus a civilian one, but that's about it.

Most of the noise probably comes from the rotors instead of the engine, anyway.


text:
Difference in lift generation for a swept wing and straight wing in subsonic condition
Would there be any differences in lift for a straight wing and swept wing (front or back) with the same airfoil cross section, same chord length, same wing span, and same area when flying in subsonic condition that is lower than Mach 3?

Since both the lift curve slope and the effective angle of attack are reduced by the cosine of the sweep angle at quarter chord, the lift coefficient of a swept wing at the same geometric angle of attack is reduced by the square of the cosine of the sweep angle.
Also, the pressure distribution over chord differs between straight and swept wings, especially near the center and the tips. All this makes swept wings less attractive, were it not for their ability to delay compressibility effects, basically for the same reasons which reduce their efficiency.
However, lift is generated in the same way: By pushing air down or by a pressure difference between upper and lower wing. Both are equivalent explanations of lift.
Only at high sweep angles and high angle of attack will vortex lift kick in and produce this pressure difference by means of a strong vortex on the upper side of the wing.
Since you ask about "subsonic condition … lower than Mach 3", I wonder whether you actually ask about supersonic flight with a subsonic leading edge. Now things are rather different between a swept and an unswept wing: While the sufficiently swept wing with a subsonic leading edge will still exhibit a pressure distribution similar to that at subsonic speed, the supersonic straight wing will create a shock, resulting in a slowing down of the flow where at subsonic speed an acceleration could be observed, and vice versa. Also, the center of pressure will move back in supersonic flight.


text:
What gas turbines have the following configuration?
Is there any jet engines--with published data on the dimension of the turbines and compressors--that are of the configuration of 2 Low Pressure compressor, 8 High Pressure compressor, 2 High Pressure turbine, 5 Low Pressure Turbine? Thank you very much!

Do the numbers refer to the number of stages?

yes, it does. Do you know any?

I couldn't find any that exactly match. The closest ones I found where
PW1000G-56 : 2-8 and 2-3
PD-14 : 3-8 and 2-6
What is the reason your looking for such specific architecture?


text:
What is the diameter of each stage of the PW800 engine compressor and turbine?
I am an Aerospace Engineering student working to analyze P&WC's PW800 engine family--specifically, the PW814GA, for a project and we need to know some hard-to-find data.
Does anyone knows where I could found out the diameter of each stage of the PW814GA fan, compressor and turbine? Or those of any similar engines so we can guess it? Thanks!

I’m pretty sure exact radius changes through a compressor or turbine are not public. Anyway it is surprising that you need this kind of data for a student project, maybe you can give us some precision about it ?

Blame my prof, what he want to do is exactly what i said. Analyze the PW800 engine. I don't need to ask this question here if I am a villain trying to do bad things.

I do not accuse you from spying at all. Analyzing an engine is broad and highly complex thats why I’m asking more details and why you need this specific dimension (seems useless for student but again I don’t know what your project is).

If your projet is literally « Analyze the PW800 engine », I recommend you to edit your question in order to ask some guidelines that we could give you to find engine characteristics: for instance, how to link By pass ratio with fan diameter, thrust, and other performance (OPR, Power, efficiency, etc..) or other interesting details for engineers


text:
How many turbine powered aircraft are in the air at any given time?
I know there are a lot of statistics about how many planes are in the air on average, but not all aircraft flying are turbine-driven. How may turbojet, turbofan, and turboprop aircraft, on average, are in the air at any given moment?

It may be impossible to answer as many smaller aircraft may not be tracked or recorded. How precise does the number have to be?

You may try to search in IATA statistics like these ones

@user39178 Right now, Flightradar24 is tracking 10,582: https://www.flightradar24.com/37.46,126.44/14 Are they all turbine powered? Probably. Are they every turbine powered aircraft? Probably not. But I don't know where you will get a better answer than that...

Hi @fooot. I believe the comment above answers without being an opinion, and uses a reference, what do you think? Regards

@Penguin most of the traffic is turbine powered, but definitely not all. And it probably doesn't include everything. But you're right that it's probably a good guess.


text:
How to calculate coefficient of drag for a particular shape?
While working on my project I gave my RC plane's nose a particular shape. It doesn't resemble any simple shapes for which coefficient of drag is provided on Internet.
I don't know simulations.  Also I don't have any wind tunnel facility for my project.  So is there any other way,  any website or any formula for computing coefficient of lift and drag?

Search for computational fluid dynamics (CFD).  I think there are open source programs that run on a PC.  Not a simple task, though.

Could you elaborate a bit on what you plan to do with the coefficient?

I don't know simulations on any software.  I also don't have much time to learn simulations.

There are essentially only two ways to do this.
First you can build a wind tunnel, run experiments and measure the forces involved.
The second is to run a computer simulation. There is software that will do this, but it is complex professional grade engineering software. Free applications are available, but I can't vouch for their effectiveness. You can search for "computational fluid dynamics software" to find options. Adding "free" to that will find you a few cost-free options.
Be aware that setting up and using this software is a complex task that involves creating a CAD model of your shape. You can definitely do the calculation if you are interested, but it's not a simple or quick task.

If you just want answer, use wind tunnel. If you want to calculate the answer, you must solve Navier-Stokes equations, with boundary conditions established to represent the shape in question. This is done using numerical analysis and is an advanced mathematical process involving complex analysis (by which I mean meaning using complex numbers and complex functions).
As mentioned in another answer, there is software available that does much of this for you.


text:
What does a pilot do if all the engine shut down in the middle of the Ocean?
In case of a commercial aircraft, what is the plan B for making an emergency landing in the middle of e.g. the North Atlantic Ocean?
I know it's very unlikely but still a possible situation. The plane is up in the air for hours above the ocean and for any reason the engines stopped working, and there's nothing near or far that could be used for landing, except the endless water.
In the unfortunate case this happened what could a pilot do in this kind situation?

Somehow related: Ditching: Fixed Wing Aircraft by SkyBrary/Eurocontrol. Some links to actual accidents.

for any reason the engines stopped working, and there's nothing near or far that could be used for landing, except the endless water.

You have answered your own question... if it is impossible to reach solid land, they attempt a water landing ("ditching"). The ideal is always to land (or "water" in this case) at the slowest possible forward speed and the slowest possible vertical speed, which are competing desires due to energy conservation (the laws of thermodynamics). At a guess, in the case of an ocean landing the pilots will accept a faster forward speed in exchange for the lowest possible vertical speed—a "belly flop" into the water is more likely to instantly damage the aircraft than a fast landing.
In the case that there is a landing strip within gliding distance, they will attempt to get to it, as one famous flight did. Aircraft do not "fall out of the sky" when they lose engine power; they are able to glide by trading potential energy (altitude) for kinetic energy (forward speed). The glide ratio of an aircraft describes how far it is able to travel horizontally per unit altitude with no engine power; for an airliner this number is in the range of around 12:1–17:1.
Of course being in this situation in the first place is highly unpleasant, so regulators make certain rules to make it unlikely. In the past this meant requiring three or four engines, or more, on transoceanic aircraft; the idea is that the likelihood of all engines failing is very low. As manufacturing has gotten better and engine reliability has increased, aircraft with only two engines are now certified to travel between continents due to a program called ETOPS. Such planes have demonstrated single-engine performance that allows them to continue to a safe landing area on only one engine from any location on their route.
ETOPS only addresses engine reliability, though. A more systemic issue, like running out of fuel, will cause problems whether the aircraft has one, two, or eight working engines.

L/D 12 to 17 sounds too small for airliner. The answer you link as argument for it gives 17 for a 747, but that's a fairly old design. Early jets start around 15 and the newest get to around 20.


text:
What is maximum acceleration that can be achieved by afterburner in level flight?
I am wondering how a fighter jet (let's take F-22 for example) would compare to other vehicles in terms of acceleration while in flight.
For cars and motorcycles, achieving 0-100 KPH in 2 seconds is doable and this means their highest acceleration would be around 14 m/s^2.
I know fight jets do not beat cars and motorcycles in the first 2 seconds of drag races and so while on ground, they do not achieve this level of acceleration. But how about a flying with an afterburner?
Is there any available data on the time required to accelerate a fighter jet from say mach 0.6 to mach 0.8 using afterburner? Can this be calculated anyhow?

The F-22 has a published static thrust of 156 kN per engine with afterburner, or 312 kN total thrust. At gross weight (29,410 kg), according to Newton's second law (F = ma), it would accelerate from a standstill at 10.6 m/s2 or just over 1 g. (This calculation ignores static and dynamic friction from the landing gear, but those forces are quite negligible in comparison to 312 kN of engine thrust.)
A jet aircraft will not accelerate faster from a higher speed than from a standstill. Jets have a thrust curve that looks like the dotted line below (source):

As flight speed increases, drag increases, but thrust doesn't (much - certainly not enough to offset drag). Therefore acceleration goes down.

That graph appears to show that thrust DOES increase slightly with speed, which IS to be expected due to higher forced airflow into the front of the engine.

@MikeBrockington You're right, and I edited the last sentence to clarify. The rate of any increase is much less than the rate of drag increase.

By the way, the linked answer has a good explanation of the factors behind the thrust's decrease, then increase, then (not shown in the graph above) eventual decrease again.

You will note the "thrust available" curve of the prop is precisely the advantage the cheetah has in the first few strides.

@RobertDiGiovanni Cheetahs have props? ;) David Attenborough missed that!

Motorcycles don't either, but both have ground contact (direct transmission of torque), which gives them an advantage off the line while the jet blows air.  So the cheetah curve will be much steeper than the prop curve, but goes to zero at around 70 knots.

Bear in mind that acceleration is determined not by thrust, but by excess Power. Excess Power is calculated using V * (T-D) / W, where D is total drag,  which decreases as airspeed increases until you get to L/Dmax, and then increases...

Also, @TypeIA, as you can see from your chart, drag decreases until you get to the bottom of the curve, (L/Dmax). After that (as KCAS increases), is exactly the area where the increase in thrust from the engine is most significant.

@CharlesBretana I'm not sure what point you're trying to make. Acceleration is determined by thrust (F = ma, where F = thrust minus drag). And drag is zero at 0 speed. At flight speeds high enough to start seeing intake compression thrust gains, drag is so much higher (and increasing) the acceleration will never catch up to what it was off the line.

It would make more sense to compare with the record holder P-42. This modified Su-27 had static thrust-to-weight around 2 (it could not be held on brakes at full thrust) and so could potentially beat most sport cars in a drag race.

To answer your third paragraph, the aircraft with the highest thrust to weight ratios have figures of just over 1, so acceleration would be around 11m/s^2 under ideal conditions (i.e. if air resistance were negligible.  However, if one were to loop a fast jet and hit full power in a vertical dive with low initial airspeed then it might be possible to achieve 20m/s^2 briefly.  But then if you drive a lawnmower over a cliff it will achieve nearly 10m/s^2 so it’s hardly a fair comparison.

The question specified level flight.

Acceleration from a standing start is based on Force and Mass until the object gains enough velocity for drag to become a considerable factor.
One must consider the increase in drag as well as the mass accelerating from Mach 0.6 to 0.8.  There is also the Mach effect with additional drag at high subsonic speeds.
The Raptors twin Pratt&Whitney F119 engines produce 2 x 26,000 lbs of thrust each dry and 2 x 35,000 lbs of thrust in afterburner.  The afterburners add an additional 18,000 lbs of thrust force.  For 60,000 lb weight, afterburners accelerate the aircraft:

18000 lbf × 4.45 N/lbf = 80068 N = 80068 kg m/s$^2$

80068 N = 27000 kg x acceleration

acceleration from afterburners = 3.0 m/s$^2$

If you had some idea of the thrust required to go Mach 0.6 and Mach 0.8 at a constant speed, then you subtract the drag penalty from the known thrust value with afterburner.  The excess thrust is available for acceleration.
The main parameters for optimal performance are minimum weight, minimum drag and maximum thrust.
From a standing start, the motorcycle (and the cheetah) will be ahead of the F-22, but not for long.
The F-22's 70,000 pounds of thrust will continue to accelerate its 60,000 lbs of mass as the cheetah, then the motorcycle reach their top speeds.
But off the line, the cheetah and motorcycle acceleration is greater than that of the F-22.  It should be noted that the best acceleration for the jet will also be at lower speeds, where there is less drag, but will never approach that of a cheetah's best.
Fast twitch muscle acceleration rates come from boxer data:
Here a 25 mph throw (11 meters/second) covers a distance of around 0.7 meter.  The average velocity is 5.5 m/s.  The distance is covered in:  1 s/5.5m × 0.7m = 0.13 seconds
The initial acceleration is 11m/0.13s$^2$ = 85 m/s$^2$
Top speed of 30 m/s in around 1.5 seconds yielding an acceleration of 20 m/s$^2$ (cheetah has least mass but also lowest thrust.  Drag factors rapidly slow acceleration).
Time to cover 100 m:

d acc = 1/2 × 30 m/1.5 s$^2$ x 1.5$^2$ = 22.5 m

d rem = 100 m - 22.5 m = 77.5 m
t rem = 77.5 m / 30 m/s = 2.6 s

Total cheetah time 100m = 1.5 s + 2.6 s = 4.1 s (hungry)
The motorcycle is 14 m/s$^2$ 0 to 30 m/s in around 2 seconds
Top speed around 60 m/s

d acc = 1/2 × 14 m/s$^2$ × 2$^2$ = 28 m

d rem = 100 m - 28 m = 72 m

The motorcycle (using gears) continues to accelerate by (estimated) 5 m/s$^2$, covering 30.5 m in second 3, and 35.5 m in second 4
After 4 seconds it's distance traveled is:

d trav = 28 m + 30.5 m + 35.5 m = 94 m

After 4.1 seconds:

94 m + (38 m/s × 0.1 sec) = 97.8 m (very close!)

Special note to Hyabusa fans:

400 m (1/4 mile) ≈ 1/2 × a × 10 s$^2$

Acceleration = 8 m/s$^2$

This racing motorbike can develop 180+ horsepower by revving to very high rpm before going through its gears. It's observed acceleration is remarkably constant.  Estimated time to 100 m:

100m = 1/2 × 8 m/s$^2$ × t$^2$

t = around 5 seconds (we're in the ballpark!)

The F-22 acceleration rate from a standing start with afterburners
would be:

70000 lbf × 4.45 N/lbf = 311500 N

311500 N / 27000 kg = 11.5 m/s$^2$

Because drag only marginally affects its acceleration at lower speeds and huge N thrust, it is constantly accelerating at 11.5 m/s$^2$.  After 4.1 seconds:

d trav = 1/2 × 11.5 m/s$^2$ x 4.1$^2$ = 97 m !

From this we can see the cheetah and motorcycle acceleration will be greater than the F-22 initially, with the rapidly decreasing acceleration of the ground competitors after a few seconds making an actual 100 meter race a very entertaining match up.  The Navy figured all this out years ago, which is why they have catapults on their aircraft carriers!

Commenting on your last sentence, yes, but does the F-22 acceleration exceed that of the motorcycle or the cheetah at any point from the standing start to reaching Mach 2.25?

From a standing start, if the F-22 has a thrust to weight ratio of 1, the motorcycle and the cheetah will be ahead.  This differentiates the concepts of acceleration and speed, jets beat anything top end (except for rockets) because they can overcome drag.  Cheetahs, motorcycles, (and props) reach a point where drag = thrust much sooner.  Always exciting in the movies when a motorcycle or car tries to stop a plane from taking off.  This is a realistic scenario.

For a cheetah, is it really drag that's limiting his top speed, or simply the ability of the animal's legs to generate more force diminishes as speed increases?  I'd be really surprised if the cheetah's top speed in a 5 knot headwind vs a 5 knot tailwind changes by anything like the 10 knot delta.  For their size, aerodynamic drag at 70 mph isn't negligible, and they can probably do a bit better with a tailwind than a headwind, but isn't it likely that groundspeed (how fast they can move their legs) is more limiting than airspeed & parasite drag for them?

I'm skeptical of the math here. A 1:1 thrust/weight ratio jet will come off the line at 1 g... surely motorcycles don't take off at 8 g? That would require considerably superhuman strength of the rider...

We now have "turbo street bikes"  running 1/8 mile (200 m) in 4.05 s.  200m = 1/2 × a × 4.05s$^2$ = 24 m/s$^2$ !

The attached chart illustrates the "Specific Excess Power" available to an F-16 at 15,000 feet MSL. The bold curves that start on the left at sea level, go upwards and to the right, peak at approximately 0.9 Mach, and then decrease and eventually terminate back at sea level are Ps curves. Ps stands for specific excess power, meaning Power per pound of aircraft. they are labeled with their respective values in units of Ft/Sec (speed) and is equivalent to V * (T-D) / W.
A formula for Specific Excess Power is:

This is equivalent to:

These specific excess power values represent the maximum combination of climb rate and/or energy gain due to acceleration, that the aircraft can achieve at the specified point in the flight envelope. Where they are negative, it represents the minimum rate of descent, and/or deceleration (from energy loss)that the aircraft will experience.
If you are in level flight, then climb rate is zero and the acceleration can be solved by
a = Ps * G / V
Looking at the diagram, it is clear that the highest Ps, and therefore the highest climb rate and maximum possible energy gain acceleration, at any altitude, occurs at or above 0.9 Mach.
This is because subsonic, as airspeed increases, jet engine power (Thrust * Velocity), increases much more significantly than total drag does, due to increased mass flow through the engine.
Energy gain, however, as pointed out by @TypeIA, is not the same thing as acceleration. This answer is therefore, not on point to the OPs question. I will leave this here anyway as, corrected, it is informative.
However, as the Ps chart is one of altitude vs TAS (Velocity), the actual acceleration (~ Ps/V) can be estimated by the slope of the Ps contours. Where they are angled at more than 45 degrees from the horizontal, acceleration is increasing as velocity increases.

-1 because the answer is factually incorrect: acceleration is proportional to net force, not power. "the highest Ps, and therefore ... maximum possible acceleration" is the key incorrect statement, because it ignores the influence of velocity on power. In other words, velocity plays a role in the calculation of power, but not of acceleration.

@TypeIA correct. You can also see from this equation in the answer a = Ps * G / V that the gain you got in Ps (which is due to the increased velocity) while the velocity is also present in the dominator and so has no effect on the acceleration.

@TypeIA you are correct. My memory of this information is now 40 years old, and is, apparently, not perfect!  We used this to calculate acceleration at points in the flight envelope, not rates of acceleration. I will edit my answer to reflect this. The maximum acceleration actually occurs wherever Ps / V are at a maximum, which, since the horizontal scale is TAS, occurs when those lines are slanted at a 45 degree angle or higher. As Robert says, the chart is really about maximum rate of *Energy Gain" whether it is Potential (Altitude), or kinetic (Velocity).

@CharlesBretana No problem, but I'm not sure I understand what you mean about 45 degree angles on the chart. I think involving energy at all only makes the question unnecessarily more complicated. But quite right that power is rate of change/transfer of energy; it's just that kinetic energy is proportional to velocity squared.

Looking further, both terms come out to fps, so, as you say, the chart can be used to determine max acceleration (with 0 climb), but apparently only for an aircraft in flight.  P still must be divided by V to get a.

@TypelA, But Power, (the rate of change of kinetic energy) is proportional to Velocity.
Robert, yes, Ps charts are for aircraft in flight, ground acceleration would be a different matter entirely. Of course, the OP is asking about in flight acceleration, not ground acceleration.


text:
Jet engine throttle-down time
Apparently airline jet engines lose ~80% of their thrust within 1 second after fuel is cut. However this seems to conflict with long throttle-down times noted in another question.
This lead to a couple of questsions:

How long do jet engines really need to throttle down?
How do they react to fuel-cut or moving the throttle to idle (see first question)
Why the difference between the two answers?
If an engine is throttling down quickly, does the rotation speed of the engine really drop by 80% within 1 second? How does it slow down so quickly, is there so much friction?

I'm mostly interested in commercial passenger transport airline engines, not GA, military, ...

The difference, whether you (or the engine management system) have the option to do it safely.

For jet engines in general, the thrust produced is not linear to the engine rpm. In fact, the percent of thrust produced decreases by approximately the 5th power for high bypass turbofan engines and 3.5th power for turbojets per N1 rpm. With such considerations, a thrust of 20% of max thrust is achieved at approximately 72% N1 rpm which is still a high rpm. The long throttle down times are because the engines still keep their angular momentum so they will keep on spinning until the friction in the shaft slows them down.

For reference: see this Aviation.SE question about thrust as function of RPM.

There’s no “throttle down” per se in jet engines.  However engine thrust does not vary linearly with spool speed and most engines operate within the 70-100% of maximum speed, with most of the thrust range between 85-100%.
In addition, there is a lag time for the engine to “spool up” from an idle power setting to effective thrust output which has to be taken into account during operation.  This is one reason that most jet aircraft have speed brakes.  They allow the pilot to maintain a higher thrust setting which allows for quicker response time to thrust lever inputs for a given airspeed at the expense of more parasite drag and fuel consumption.  Critical areas of flight such as VFR patterns, instrument approaches, short final, and go arounds, where near immediate thrust response is required makes this a useful flying technique in jets.


text:
Are there more accidents in winter months, and if so, why?
I was watching The Flight Channel videos and have noticed that the accidents seem to happen more often in winter months (for the Northern Hemisphere). Are there some statistics to back this claim?
It seems logical: Winter months means icing on wings, slippery runways, etc. Are there any not so obvious reasons for the increased accident rate during winter?

You can have icing in the middle of the summer, too, even without going to extremes. At about 2 deg C colder per 1000 ft altitude, if the air temperature at ground level is +20 C (not unreasonable in the summer months at latitudes where you get below freezing temperatures in the winter), at 10k ft the outside air temperature is around freezing. Add a bit of moisture to that and you get icing pretty quick.

@aCVn Indeed. And for aircraft that fly at higher altitudes, sub-freezing temperatures happen on virtually every flight. It's interesting watching the OAT on the in-flight entertainment displays on an airliner in the summer. It may be 100+ degrees F on the ramp and still be well below 0 F at cruising altitude.

You can review dates of when accidents happened here
https://www.ntsb.gov/_layouts/ntsb.aviation/index.aspx
and determine which time of year more events occurred in. I am not going to compile that for you.

Accidents are rarest in winter.
In https://www.ntsb.gov/_layouts/ntsb.aviation/index.aspx, click "Download all (text)", to get a file AviationData.txt containing 80,000 accidents and 4,000 incidents.
Keep only the Accidents, split the |-delimited fields to get mm/dd/yyyy, then split by / to get the month, then count how often each month appears.  From a Linux shell:
grep Accident AviationData.txt | awk '{split($0,a,"|"); print a[4]}' | awk '{split($0,a,"/"); print a[1]}' | sort | uniq -c
Result:
   4439  01
   4697  02
   5989  03
   6632  04
   7838  05
   8758  06
   9806  07
   9223  08
   7607  09
   6267  10
   4922  11
   4485  12

Accidents are rarest in January, become smoothly more frequent until July, and then become smoothly rarer until December, i.e., the subsequent January.
But is this trend just because summer has more flights?
Let's compare apples to apples,
instead of 747s to everything including powered parachutes.
This table shows that airline passengers have the same trend,
about 26% to 31% more in July than January.  Numbers that big argue that airline flights have the same distribution.
When filtering AviationData.txt to include only Boeing, Airbus, etc,
July is about 90% more than January.
So summer has 30% more flights than winter,
but 90% more accidents.
Even after adjusting for this, an airliner flight in winter is only a third as likely to have an accident as a flight in summer.

Ill second Camille's answer and add the missing factor of GA vs. Commercial Aviation. The NTSB makes the 2012-2016 data available in spreadsheet format here. If you download that and combine all the accident data you will see that the overall accident data for those years, plotted by month looks something like this:

This data set for even the limited years is in line with the other answers larger data sets. But if you limit the data set to only part 121 accidents the trend disappears:

For those years April and September were the Safest months to fly but a trend really cant not be observed here.
So why does GA cause so many summer accidents? Well its simple, *most GA planes dont have ani/deice equipment so winter flying in the northern parts of the country is out of the question for many GA pilots. The simple fact is there are substantially more GA flights in the summer.


text:
Are the A380 engines interchangeable (given they are not all equipped with reverse)?
I have noticed that the A380 only uses the two engines closest to the fuselage to reverse thrust to brake. Are all four engines the same (i.e.: could they theoretically swap engine 1 and engine 2) or are the inside ones different from the outside ones?
In general, would the outside ones have reverse capabilities if they were installed on the inside or are they different types of engines?

I don't believe that the outboard engines have thrust reversers installed, if that is what you are asking. Hopefully somebody has a reference for that.

This question discusses the A380 outboard thrust reversers, or lack of. My understanding is that the thrust reversers are more properly considered part of the nacelle, and there is some integration required to link them to the engine systems. If someone knows better I'd be interested to know more.

Would the failure of one of a pair of outboard reverse thrusters cause a more severe turning force and compromise the landing safety?

@Transistor The reason for only inboard reversers that I've seen cited is that there's a higher risk of FOD ingestion when using the outboard reversers, given the A380s large wing span. But yes of course, physics alone dictates that the thrust differential has a greater "lever" if the engines are farther out from the body.

The Airbus A380 comes with two engine choices:

Rolls-Royce Trent 900
Engine Alliance GP7000

The thrust reversers are not part of the core engines. The reversers are developed by the company which produces the engine nacelle, in this case Safran Nacelles. They developed nacelles for both engine variants for the A380, including the first electrically actuated reversers:

Safran Nacelles nacelle systems equip the Airbus A380 powered by four Rolls-Royce Trent 900 engines or four Engine Alliance GP7200 engines. [...] they are the first in the world to have a thrust reverser with an Electric Thrust Reverser Actuation System (ETRAS®).

(source: safran-nacelles.com)

(image source: safran-group.com)
Are the nacelles interchangeable?
No, the nacelles for the outer engines are different from the inner ones to save weight. This article says:

Four nacelles were developed for the A380: one inboard nacelle (with a thrust reverser) and one outboard nacelle (without), for each of the type's two engines, the Rolls-Royce Trent 900 and Engine Alliance GP7200.

As ymb1 pointed out in the comments, this is confirmed by the type certificate for the Trent 900:

At engine certification, the engine has been approved for use with Aircelle Thrust Reverser Unit
  (TRU) at the inboard engine positions (part numbers ASE 0010-XX-0 for the left hand installation
  and ASE 0050-XX-0 for the right hand installation) and for a Fixed Fan Duct (FFD) in the outboard
  engine positions (part numbers ASE 5010-XX-0 for the left hand installation and ASE 5050-XX-0
  for the right hand installation).
  The TRU and FFD do not form part of the engine type design and must be certified as part of the
  aircraft type design.

and also for the GP7000:

This engine is approved for use with Airbus thrust reverser system P/Ns (left and right)
  L78DR130000xxx / L78DR230000xxx and with Airbus fixed fan duct P/Ns (left and right)
  L78DR140000xxx / L78DR240000xxx.

Got it, thank you! My naive self was including the nacelles as part of the "engine" when I asked the question.

It sounds from this answer like the actual answer to the question is yes, the engine cores can be moved from one nacelle to another if need be, since the type cert for the GP7000 says that it's approved for use with any of the 4 nacelles on the A380. Just the nacelles themselves couldn't be moved around (which they normally aren't anyway.) Am I reading that correctly from the answer?

@reirab Yes, that would be my interpretation as well. But I don't know if there are any small differences (under the same type cert) that would make moving to a different position impossible (see also John K's answer). Anyway, it is not impossible to move engines because of the reversers.

If your interpretation is the engines are interchangeable, then this should be mentioned in the answer, as for the moment it only states the nacelles aren't interchangeable, and therefore doesn't answer the question explicitely.

@reirab: The engine cores and the fans.

@Sean Good point; I should have mentioned the fans, too.

Airlines normally maintain what are called Engine Build Units (EBUs) in their spare engine pool.  The engine will be pre-assembled up to the point where variations in position on-wing have to be accounted for.  Components beyond that point are only installed at the time the engine is installed on-wing.
Designers try to minimize engine "handing", mirror image configurations of things like plumbing, heat exchangers, etc, so the EBU can be built up to the most complete assembly possible, ready to be slapped on in a crisis.
On something like the 380, to the extent that reverser related components can be installed on the EBU, the airline will probably have a choice of:

Leaving the reverser related components off the EBU, so a given EBU from the spare engine pool can be installed on any location on-wing.  Cheaper from a spare engine pool perspective.  Or:
Maintaining 2 EBUs, one for inboard installations with reverser components installed and one for outboard installations, without reverser components.  More expensive, but could be a significant time saver.

The choice will be based on a global cost business case.

Good information! How much of the reverser is actually installed on the EBU, though, since the reverser is part of the nacelle, not the engine core?

Hard to say without knowing the engine itself.  There will certainly be control components of some sort related to the thrust reverser system; sensors, actuators etc. If the engine is non-FADEC (not in this case I know) there is often a some sort of actuator that snaps the throttle control to idle if the reverser deploys in flight.  On a FADEC engine it's done by software.  It could be though, that so much of the reverser system is independent of the engine itself that a single EBU is worth having for the entire fleet that there is not enough time saving during a installation build up.

The sensors are not really a commonality issue. All that is needed on the non-reverser nacelle and pylon is an interface to the FADEC which mimics the fact that the (non-existent) reverser is not deployed. It's worth pointing out that with FADEC the majority of the engine hardware (up to the level of complete engine modules) can be common even between different mark numbers  of engine on different aircraft types. This is analogous to a common powerplant being "re-chipped" for different applications (with different tradeoffs between service life and performance) in the car industry.


text:
Why do Boeing planes have more flap settings than Airbus planes?
The Boeing 737 and Airbus A320 are similar in size and performance. They are direct competitors. Boeing seems to have eight flap settings (1, 2, 5, 10, 15, 25, 30, 40) whereas Airbus seems to have four flap settings (1, 2, 3, Full).
What is the reason for Boeing having twice the number of flap settings? I believe it is similar on other models as well.

Interestingly, the trend seems to be continued for the newer models. The Boeing 787-9 has nine different flap positions, despite being a new and clean design. The similar Airbus A350-900 continues to use the standard 4 Airbus settings.

And some older Mooneys have infinite flap settings depending on how much you pump them up...
The reality is that there are no regulations on how many flap settings an airplane must have and on an airliner that may also have things like speed breaks or slats as well, flap settings may vary by design or simply by engineering choice.
Flaps are used for improved short field take off as well as to make a steeper approach at a slower airspeed. If Airbus can achieve desired performance with 4 settings there is no need to complicate matters and add to pilots work load.


text:
How are parallel runways named if there are more than 2 or 3?
I know that it's very common for runways to have a parallel neighbor, and they're normally called left and right. I have also seen some runways called "center" if there are three parallel runways.
What would happen if there were more than that? Is this even possible?

thanks, sorry about that


text:
Why doesn't the black box also record video?
Why does the black box still only record the cockpit's audio today, rather than also recording video of the cockpit? Wouldn't a video of the pilots' actions and what they were seeing outside the plane be very helpful in determining what caused an accident?

A video camera on top of the tail looking forward would make a lot more sense.

In the United States, the FAA at least as far back as the 1980's pushed for cockpit video. Pilot unions and their lobbyist have been successful in defeating it. The FAA has attempted in several test cases to use audio & data recorders to prosecute non-crash violations and understandably the thought of video scares pilots. I believe it will soon be enacted because people are becoming more accustom to privacy invasion. Police video, grocery stores, gas stations, apartment buildings, traffic and security cameras and even automobile cams are common place in most countries - including Russia.

Why continue to call it the "black box", when everyone knows it is orange and the name is CVR to distinguish it from the FDR? Possible duplicate of If we add a video recorder in the cockpit to complete FDR/CVR, will we add a blackbox? which was closed as opinion-based.

@jwzumwalt That comment sounds like the start of a good answer, why not expand it to one?

There pilots actions can be reconstructed pretty well using the noises from the cvr and the data from the fdr, so what does video give you?

@Ron Beyer example: was the crew passed out when they didnt touch the plane for 30 min or did they have quiet laptop keyboards!?

@TomMcW: This other question is about recording the cabin, not the cockpit :-)

@mins You're right. I swear this has been addressed before, but maybe not

@TomMcW Maybe you're thinking of this (closed) question?

Why does the black box still only record the cockpit's audio

The Black Box
There isn't a single black box. There is normally a Flight Data Recorder (FDR) and a separate Cockpit Voice Recorder (CVR) in large civilian transport aircraft. These are not mandatory in military transports or smaller aircraft.
Under proposals made in the last decade or two there would probably be a separate video recorder that records the flight instrument panel, recording what information the displays are showing the pilots and the positions of switches. So far as I can find, there are no official proposals to record external views - which are usually likely to be much less useful in determining the cause of an incident if you have FDR and CVR data.

Opposition

the National Transportation Safety Board in the United States has proposed the idea of featuring cockpit video recording in airliner cockpits several times since the year 2000. However, such proposals have largely been opposed, especially by pilot unions who view such a stipulation as an invasion of privacy. NTSB has never been met with support for such a requirement from the FAA, since first proposing it in the year 2000.

(my emphasis)
From ICAO is Not Calling for Cockpit Video Cameras in New Airplanes. Aviation Today. 2017.

Pilots don’t see the disappearance of Flight 370 as a reason to embrace cameras. They cite two reasons for their opposition: Video surveillance will almost certainly be misinterpreted or get into the wrong hands, and it can adversely affect how they do their jobs. “What a camera can capture can be so easily misunderstood and misconstrued,” says Doug Moss, a former test pilot and accident investigator.

From Why Pilots Hate the Idea of Cameras Watching Them Fly. Wired. 2014.


text:
To use the equipment suffix "G", does the GPS have to be certified for IFR?
To use the equipment suffix "G", does the GPS have to be certified for IFR flight?

What equipment suffix are you referring to?

See list of FAA equipment codes here or here

@selectstriker2 /G is the equipment suffix used in FAA IFR flight plans for GNSS plus mode C

In the US if you are just getting flight following, you can use the /G suffix when making your request to ATC. However, in 20 years of using flight following on almost every flight, I have never had ATC give me anything but a heading to follow so it really doesn’t matter what you use.

@JScarry That's interesting, why do you include equipment details in a fight following request?

@Pondlife That’s how I was taught 20 years ago and I never thought about it. I guess it’s a carry-over from filing a VFR flight plan when I was a student pilot. I’m guessing that back then there were still aircraft that were Mode A, so it was good to let ATC know that you were transmitting altitude. I probably don’t need to do it anymore since everyone is Mode C or S and lots of planes have ADSB.

@JScarry Thanks for sharing that. I think you're right about ATC making assumptions. I rarely hear pilots include their equipment suffix in a pop-up IFR request and ATC never asks for it. I guess they're just assuming that everyone is /G.

Yes, using GPS for IFR requires a certified unit. The AIM 1-1-17(b)(2) says (emphasis mine):

Authorization to conduct any GPS operation under IFR requires:
(1) GPS navigation equipment used for IFR operations must be approved in
  accordance with the requirements specified in Technical Standard Order
  (TSO) TSO-C129(), TSO-C196(), TSO-C145(), or TSO-C146(), and the
  installation must be done in accordance with Advisory Circular AC
  20-138, Airworthiness Approval of Positioning and Navigation Systems.
  Equipment approved in accordance with TSO-C115a does not meet the
  requirements of TSO-C129. Visual flight rules (VFR) and hand-held
  GPS systems are not authorized for IFR navigation, instrument
  approaches, or as a principal instrument flight reference.


text:
Where to find information on weight breakdown for helicopters?
I would be interested in information on the weight breakdown for the different components of a helicopter. How much of the maximum gross weight is related to the airframe, engine, gearboxes, transmissions, rotor systems, avionics, etc.
Could someone point me to a data source where i can find such information?
I already found a very reliable source on technical specification of helicopters in the Type Certificate Data Sheets published on the EASA website here:
EASA TCDS List

Helicopter Performance, Stability and Control by Ray Prouty has a section on weight estimates on page 663. A few of the equations, rest are in the book:

I'm afraid Mr. Prouty used imperial units.

FWIW, for military rotorcraft, there are the AFDD Weight Models mentioned in NASA Design and Analysis of Rotorcraft (NDARC) (page 159).


text:
Is a turboprop or a turbofan more eco-friendly?
If we compare them, which one wins? Why? And, what about CO2 emissions?

Related: Which engine is more efficient between turboprop vs jet?

Global warming isn't top of your worries when you have all the planes dumping all the toxins, pounds of lead per GA airplane per hour for starters.

Yes. The answer is yes.

"There is still up to 0.56 g/litre of lead in Avgas 100LL." https://www.shell.com/business-customers/aviation/aviation-fuel/avgas.html  So that's ~2g/gallon, 0.0044 pound, or 0.044lb/hour when burning 10 gal/hour (my plane for example).  Larger GA planes, the kind that are turbine powered, run on Jet A, and not on 100LL gas.

Two worlds
There are two elements constraining propeller use:

The thrust we can get from a free propeller is lower than from a ducted fan at the same airspeed.
Propeller efficiency quickly decreases with Mach number.

Propeller performance vs speed. Source
For these reasons fans are the natural choice for large and fast aircraft, and propellers for slower short-haul aircraft (typically regional aircraft like ATR 42/72 or Dash 8).

Is a turboprop or a turbofan more eco-friendly?

What is eco-friendly? E.g. do you consider cruising altitude and noise?
As both aircraft are using aviation fuel, the less fuel used, the less emissions, if this is what you mean. This is a matter of efficiency, which is slightly in favor of turboprops.

Efficiency of engines. Source
The difference comes from the efficiency of the propeller (80%) compared to the fan (65%).
Turboprop aircraft could technically be used for long haul flights with an increased flight time, but shorter flight times have the preference from airlines (less aircraft, less pilots, passengers more satisfied).
Due to the engine choice, it is usually not possible to fly the same trip using both engines, which means we are unable to compare actual flights with their actual weather, seat use ratio or wait times, all important factor in fuel consumption.
While engine efficiency is important, a more important element is about the fuel consumption per passenger. While I haven't searched for accurate numbers, a large turbofan aircraft should be more efficient than a smaller turboprop in the end. That was the idea behind the design of the A380. As life has shown, you may not want the lowest theoretical fuel consumption per passenger either.
Indeed fuel rate and emissions vary with engine mode, and is different between phases of flight. To make things comparable, ICAO has defined a way to report numbers, mixing different phases.
If you need accurate information about engines emissions:

For turbofan (jet) engines: ICAO Aircraft Engine Emissions Databank, an ICAO databank hosted by EASA.
For turboprop engines: Swedish Defence Research Agency can provide information on request about emissions (NOx in particular).

The good news is: EU plans to grade aircraft according to emissions.

What about CO2 emissions?

Turboprop and turbofan engines are similar from the engine point of view, they are turbine engines based on the same Brayton cycle. This is the typical emission split for a turbofan as found in the European Aviation Environmental Report 2019:

 Emissions from a typical two-engine jet aircraft during 1-hour flight with 150 passengers. Source
Efficiency improvement
The main factor leading to low efficiency of aircraft engines, comes from the fuel engine principle, the thermodynamic cycle is merely 50% efficient. The next step in aviation is to use electric motors, but this is a technology currently, and likely for a long time, impossible to deploy on large aircraft. The is a domain highly researched.
In the meantime:

Improvements are made on turbines. See, for example, the site of the Clean Sky initiative, a public-private joint undertaking under EU auspices.
Hydraulic and pneumatic devices are replaced by electric devices, to reduce weight and maintenance costs (More Electric aircraft).

Propfan
As usual in engineering, hybrid solutions are effective trade-offs. A good illustration is Safran trying to get the best of both worlds, experimenting a mix between propeller and fan, the propfan, a propeller, or rather a unducted fan, which can work at higher airspeed: The Open Rotor.
The idea is not new, and was part of the Hamilton Standard + NASA research program in the 70s and 80s, following the oil embargo. However there is a difficult problem to solve: A propeller rotates slowly compared to a fan (1,000 vs 5,000 rpm), it needs a gearbox on the engine output shaft, or a slower engine. Slower engines and efficient gearboxes for high power are difficult to build.
See more about rotation speed and gearbox in Is it possible to drive a prop directly from a jet engine without a gearbox?.

Safran Open Rotor. Source
Different goals are sought, and a solution for a goal often opposes another goal. What may be valid for fuel efficiency may be a bad solution for noise reduction, or for NOX reduction.

Welcome back, very well composed answer.

Hi @Koyovis, thanks a lot.

Note that the problems with high-power gearboxes have mostly been worked out, to the point that good-sized geared turbofans are now on the market.


text:
How do propeller planes suddenly make noise?
I was wondering: how can a propeller plane, single engine or otherwise, be flying along relatively silently and then start making noise, often very loud--and then turn it off just as quickly? Are they descending/ascending? It seems like the engine must be straining.
Thank you.

Engine noise is a very small portion of the total noise of a propeller (or rotor) aircraft. Propeller tip speed seems more likely to me to be a determining factor, especially as the propeller tips approach the transsonic region.

When flying or when taxiing?

When flying overhead...I see planes that are able to turn the noise on or off--without appearing to be making dramatic movements.

Welcome to aviation.SE! If you're close to an airport with a lot of flight training, you may be hearing aircraft in the pattern making power changes as they take off at high/full power then reduce it again for landing.

It is unusual to change prop speed quickly and only briefly, so I would suggest two possible explanations:

On the ground: The pilot tests the propeller pitch control. This he/she does by revving up the engine while the propeller is at a low pitch setting. Then the pitch is increased, which increases the aerodynamic forces on the prop and, consequently, the noise it radiates out. Since this test takes only a few seconds, the result is just what you described (but not while flying overhead).
In the air: Propellers don't radiate noise equally in all directions. This is especially pronounced on the T-6 "Texan", where the noise intensity increases dramatically when you stand directly abeam of the aircraft. The plot below is taken from this report on propeller noise. Probably what you hear is caused by the variation in noise (and dominant frequencies) while the plane flies overhead.

Directivity plot of propeller noise. The details depend a lot on the specific aircraft and propeller type.

Most of the noise of a propeller plane comes from the propeller tips. And an easy way to change the noise is to change the tip-speed, either suddenly up, suddenly down, or gently.
People on the ground notice the change in the noise of an airplane, so if you need to change the propeller speed, it's best to do this gently so there's no sudden 'whoosh' of the tips.

It could simply be that the plane is passing you at a high-ish speed, at a high altitude. The plane is high up and moving fast, and it takes a second for the sound to hit you, The you hear the sound and the plane is gone, then the sound cuts out.

It could be... but then again, it could be a lot of things.


text:
Do aircraft carry commercial VHF radios?
Years ago, I was working in the bush and we used portable radios on something like 154MHz. When it came time for pickup, we were able to talk to the helicopter pilot on that frequency. Since it's outside the air band, I'm wondering if it's normal for aircraft to have VHF radios installed to cover commercial (and maybe amateur) VHF bands.

Was he a company pilot or one specifically contracted to do the drop/pick? If so, the VHF radio may have been part of the agreement.

Contract helicopter, who worked for many clients, all presumably with their own frequency allocations. My impression was that the pilot could dial in whatever frequency was required to talk to the ground. It certainly made operations easier and safer, but the helicopter must have had a radio connected into the aircraft in order to use the PTT on the stick.

154 MHz could make it one of the MURS frequencies, which are license-free (actually, licensed "by rule") in the US. So anyone can have and use such a radio, for commercial or any other purpose--far less restrictive than Amateur or licensed commercial. However, I see one reference that says "MURS operation is NOT authorized aboard aircraft in flight".

No, is the short answer. Aircraft generally only carry radios covering the bands they require as standard - i.e., those covering aviation communications and navigation. I have an airband transceiver here and it can't physically be tuned that high. As far as I know, the ones in the planes I fly are identical.
I can't see any advantage in doing otherwise, as standard, as the vast majority of pilots are not licenced to talk on such bands.
In terms of citation, here's a popular general aviation radio, the BendixKing KX 165A
https://www.bendixking.com/en/products/nc/navigation-and-communication/kx-165a

Communication Transceiver: 118.000 MHz to 13.975 MHz in 25 kHz
increments, 118.0000 MHz to 136.9916 MHz in 8.33kHz increments
(118.000 - 136.990 displayed per DO 186a and ED-23B) (8.33 kHz capable
KX 165A only) Navigation Receiver: 118.00 MHz to 117~ .95 M

And, here's another:
https://icomuk.co.uk/IC-A220T/Panel_Mount_Aviation_Radio
(From the manual: https://icomuk.co.uk/files/icom/PDF/productManual/A220-TSO-Instruction-Manual.pdf)

Frequency Range: 118.000 to 136.992 MHz (8.33khz)

Bendix has quite a few typos in their own specifications: that should be "to 136.975" instead of "to 13.975" and the navigation range should start at 108 MHz, not 118.

Good answer.  Some airplanes carry additional radios but, even then, they are usually required for some kind of normal operation.  I had the pleasure of flying a plane with a HF radio and could pick up all kinds of strange stuff.  Pro-communist Cuban propaganda was a notably strong transmission (Radio Havana; english).  And this was while flying over Wyoming.

OTOH helicopters often need to talk with ground personal, which is not trained for aviation communication, nor have such transmitters. Firefighters, but also construction works, transport of goods (e.g. woods). Note: low altitude, low speed

@GiacomoCatenazzi I'd argue that's simply mission specific equipment. There's nothing inherent about helicopter operations that means they need such radios. Your average off the shelf GA Helicopter will be airband only

In Canada, its normal for utility helicopters to be equipped with "agile*" 2m commercial band radios to communicate with the ground, often on a clients Licenced commercial radio channel. almost all oil/gas, forestry work, and firefighting relies on air to ground communications, usually to people without an aviation radio licence
*agile refers to it being capable of changing frequency manually, normal commercial radios need to have pre-programmed channels and cannot change to un-programmed channels.


text:
High altitude turbine efficiency question
The simple reason turbine engines are more efficient at high altitudes is because as the air becomes less dense it requires less fuel as the ratio has to remain constant.  This holds true up to isothermal temperature which is usually at 40,000 feet.  The turbine compresses the colder air with less fuel required and you have a much lower fuel burn.

Welcome to aviation.SE! What exactly is your question?

Maybe you wanted to ask this here.

This isn't true. Less dense air at higher altitudes means less oxygen to burn with the fuel. Less burn means less thrust. In the limit of no oxygen, there is no burn, and no thrust at all.

right, and efficiency is improved because ambient temperature is lower.


text:
Why isn't the bell distribution used?
Why has the bell distribution not become widely used? Is the bell distribution only ideal in inviscid flow scenarios or is there another reason for the lack of use?

Are you talking about Figure 2 on page 4 of this NASA document?  https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160003578.pdf

Yes and also shown in Figure 1 (a -1933) in the same publication.

Something like it is widely used, only not by this name.
Although less elegant and general than Prandtl's paper, the same solution was found 17 years later by R.T. Jones when he optimized the ratio of lift to mass of wings in NACA TN 2249. The figure below is from the concluding page of this report.

However, induced drag is not all. By increasing span, wing surface area is also increased which will increase viscous drag. Therefore, the optimum really is a combination of both; having the least amount of wetted surface for the most net lift (total lift minus wing weight). This is somewhere between an elliptical and a triangular load distribution where size also matters. Small aircraft are closer to the elliptical distribution whereas large aircraft tend more to the triangular one. Negative lift at the tips only happens with extreme span to elliptical span ratios (note the curve for S/S$_\text{e}$ = 1.30). Negative lift as in the bell-shaped lift distribution, however, is a prerequisite for the Horten type of flying wings because it allows to create proverse yaw. If you have a multi-engined aircraft and need to size the vertical surface for the engine-out case, covering adverse yaw will be trivial and there is no need for a true bell-shaped lift distribution.

You are wrong, Bell distribution dont has negativ lift at tips..

@ROTOR Better think before you type. Look at it at different angle of attacks. Especially, study the Horten bell distribution. Who is wrong now?

you are wrong.when flying in  design- range,wingtips allways produce  small lift..listen at 20:58-22:00   https://www.youtube.com/watch?v=RoT2upDbdUg

@PeterKämpf, the CFD studies by J Murillo, and previous paper by Al Bowers seems to suggest the lift force reduces to zero at the tips over a wide range of angles of attack (granted the CFD study is interested in stall analysis so shows detail from AoA of 0 degrees to around 20), Figure 20 in the flight validation paper by Bowers et al shows negative loading only at an elevator deflection of -4 (it's a flying wing so those are elevons). I can send links to these papers if that is helpful? What am I missing?

@AlastairWyllie The lift force will only be zero over a wide angle of attacks if either you measure directly at the tip or if chord is zero. Near the tip the angle of attack will of course change the lift; less than in the center, but still markedly. Or all aerodynamics so far has been wrong. If you want the lowest bending moment, you need to design for the max alpha case. At lower AoA lift will go down over the whole span, and if it was near zero at max alpha, it will become negative at practical AoAs.

@PeterKämpf, that makes sense, that explains fig. 20 in this paper: https://ntrs.nasa.gov/citations/20210014683 this shows elevator deflections at a cl of 1.16 using vortex lattice. given that this paper: https://ntrs.nasa.gov/citations/20180006832 predicts stalling at around cl max near 1, that makes sense I guess. On page 7 of the first paper I think that suggests the design Cls for the Prandtl-D1&2 are about 0.6. Thank you!

@AlastairWyllie Thank you for the links! Prandtl himself in his paper used the findings to explain the much higher taper ratio of contemporary designs (which do not fit well with an elliptical circulation). This makes a sentence like the creation of aircraft using the Prandtl bell spanload will require considerable new techniques rather odd and sensational. This devalues the whole paper - after all, what it tells us has been common knowledge for almost a century by now.

i think the short answer to your first question is that there aren't very many aircraft without vertical surface. Only a few body-style such as flying wing come to mind, i have a friend who designed one recently.
For your second question no unless you're approaching the speed of sound, "inviscid flow" simplifies equations by omitting complexity with negligible effect where the flow of fluids with low values of viscosity can be assumed. i would say in practice you would have to describe a very specific scope within which your function would be considered ideal.


text:
I flew the wrong pattern at an uncontrolled airport... Should I be worried?
Ugh... I'm beating myself up as I feel I made a pretty serious mistake over the weekend. I'm a PPL trying to build up XC hours trying to work towards my instrument. Over the weekend I did a short XC to an extremely remote desert airport which is a nice little flight. I do flight following all the way there, uneventful. 15 miles out I get the ASOS and it says winds calm. After canceling flight following, I switch over to the CTAF.
This is where I started to get a little overwhelmed and I start making mistakes. I had waited a little longer to start my descent so I was approaching a little faster than usual. I have made this flight several times before and the winds are usually from the east so I planned my normal pattern entry to cross the field, make a right turn and enter the left pattern for the easterly runway. As I'm approaching I'm using my standard communications; someone on the ground radios to say the winds are actually out of the west and at at least 10 knots as the windsock is almost straight out. At that same moment, another pilot radioed announcing they were 3 miles to the west and inbound to land. For some reason this last minute information really overloaded me and I just went into autopilot. For some reason, I still just had "left pattern" baked into my brain. Instead of continuing to cross the field I entered at a 45 into a left pattern for the westerly runway. (sigh). I fly it normally and on final the traffic that was a few miles out now announces they are on a right downwind. My heart sinks. I realized my mistake, and although I am mortified, I decide to continue the landing and go on with my trip back to my base.
Afterward, I debriefed myself trying to isolate what happened, and how to prevent this kind of mistake again. I take safety and procedure very seriously. I shudder to think what might have happened if there was a NORDO in the pattern...
My question is should I be worried? I've never made this type of mistake before and am frankly expecting a call from the FSDO. It's not a populated area and there is very little traffic there but still...

How do you cross the field and then make a right turn to enter a left-hand pattern?

This is a regulation that pilots often deliberately break for navigational convenience. As long as you don't hit anyone or piss off the neighbors with noise, nobody cares. Keep your eyes out the window!

Re: the pattern. I was trained the proper approach is to cross the field, make a wide right 270 that puts you on a 45 degree angle to enter left downwind instead of just turning left into the pattern.

Don't psyche yourself out. 1) Everyone makes little mistakes. Otherwise you won't learn anything. That's why the FAA wants you to have all those hours... so that you make the little mistakes and learn from them. 2) You can file an ASRS form and immunize yourself from enforcement action. 3) The FAA's "compliance philosophy" means that while they might talk to you about little accidental infractions, they won't take action unless you can't show them you have a safety/compliance philosphy.

@Dave-CFII Submitting an ASRS does not "immunize" yourself from enforcement action. The FAA says that if you submit a report it will not impose fines/fees for certain violations but that doesn't mean that they won't take other enforcement actions. In the OP's case I doubt that anybody is going to care, but don't think an ASRS is a "get out of jail free" card.

If it's "an extremely remote desert airport", who would be around to notice?   Indeed, I'm surprised that there was anyone on the ground or inbound.

Thank you all for your feedback! re: the remote airport, it is still a large airport which is towered during the week, however, my base is an extremely busy airport so, by contrast, I guess it seems extremely remote. It is usually pretty empty. re: the ASRS, I have gone ahead and submitted one, whether or not I am reported and it protects me, submitting it helped me type out exactly what I learned and what I'll be doing to ensure it doesn't happen again.

So he was on a right downwind because the traffic pattern is displaced to the North always? Left hand for (for example) RWY 09 and right hand for RWY 27? Is your concern overflying some airspace that is not part of the pattern, or a conflict with the other aircraft? If it was the other aircraft, did you coordinate with him for one of you to extend the downwind and sequence behind the other? That'd be the thing to do. Otherwise, no harm - no foul is what I say.

Yes, my concern is flying the opposite side of the pattern. (south of the runways) in left traffic for 27. I was communicating all of my legs and am positive the other pilot knew where I was at. My main concern is accidentally flying a non-published pattern. It did not cause me to fly into any restricted airspace or fly too close to anyone or anything.

Don't worry about it too much.  Are you specifically asking what are the odds of getting a phone call about this?  I'm not sure this is a really good question for Stack Exchange.  If you are really worried about it, fill out one of those mistake-reporting forms just in case -- https://asrs.arc.nasa.gov/
Newish/ overloaded pilots at unfamiliar airports have been known to overfly the field, look at the wind sock, and then proceed to set up a landing in exactly the wrong direction.  It happens.  Try to be aware of when you are getting over-loaded and double-check yourself.
Live and learn-- you lived, so learn.

You are probably correct this is the wrong forum, but I don't really have a community in aviation so I'm just looking for resources where I can. Thank you for taking the time to reply.


text:
How useful is skyscrapers and high buildings lighting to get a visual reference for pilots by night? (not obstruction lights, just general lights)
I would like to know how useful is skyscrapers and high buildings lighting to get a visual reference for helicopter and small planes pilots by night in cities like New York. This is different from obstruction lights. I'm talking about shapes and colors.

While opinion-based, IMO this question is worth keeping

Somewhat related: Can small planes see lights on the ground?

Buildings and their lights can be very useful to aircraft in VFR conditions at night to orient themselves regardless of the type of aircraft.
Three building lighting examples that I often used were:

When flying Metroliners for a commuter airline that operated to Walla Walla, WA, I would call for a visual approach to the airport when I saw the Washington State Penitentiary. It's distinctive pattern of bright lights, especially those around its perimeter, made it stick out like a sore thumb.
When flying night freight in 727s, from many miles out, we could see the blue neon lighting outlining the Sofitel Hotel just across the road from the southwest corner of Miami International Airport.
Back in the late 1990s, the high rise hotels along the beach at Tel Aviv had a distinctive pattern. Head just to the south of them and you were lined up for Ben Gurion airport when approaching from the west.

Really, if you go into most urban airports regularly at night, you learn to recognize the pattern of the lights and can use them to orient yourself.
Freeways with heavy traffic are also helpful. Interstate 5 running south from Albany, OR to Eugene, OR has a 33 mile straight stretch that produces a line of headlights. Aircraft approaching from the north can aim about 15° right of that line and be headed to the Eugene Airport.

Another example is flying into Reno from the north: the approach end of the runway is located between two brightly-lit, ~30 story hotel-casino buildings.  Coming from the west in a small plane, you follow I-80 and hang a right at the MGM :-)

Of course, relying on visual cues alone can be potentially dangerous...

Lights at night can be useful in VFR conditions, but if conditions are less than ideal, it can be dangerous to rely on external lights.
For example, if its pitch black and you can see a light which you think is on the ground near the airport and actually its a star?
Spacial disorientation can occur very easily in poor visibility. This is the top google search result just now http://hartzellprop.com/5-tips-avoiding-spatial-disorientation-night-flying/
I would say having some instrument flying skills even if you are not instrument rated is a good thing for night flying.
If an area is very dark with no lighting whatsoever, are you sure where you are? The dark area could be a mountain that you are about to run into.
If you are on final approach and the runway lights go out, you could have descended too far and there is ground between you and the airport.
Night flying in anything other than perfect VFR conditions can be challenging especially if the pilot doesn't do much of it.

It's pretty easy to tell the difference between stars and ground lights.  What can get rather disorienting, at least in my experience, is flying over places (like parts of Nevada) where you can see only one ground light.  It seems to hold my attention, without being much use for orientation.

In addition to the direct visual references provided by building and street lighting, in major urban areas the overall light pollution often  provides enough light to see terrain and unlit obstructions. I commute across the Los Angeles basin by Lancair daily, and if it's overcast or slightly hazy the reflected and scattered city lights provide almost as much general illumination as one would get from a good moon on a clear night in an unpopulated area.